Fuel supply system for internalcombustion engines



S. G. HOOKER ET AL Aug. 1, 1950 FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed April 8, 1947 2 Sheets-Sheet 1 i\\ .T 7131' QQ 5M 425 022; 6

Aug. 1, 1950 s. s. HOOKER ET AL FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed April 8, 1947 2 Sheets-Sheet 2 Patented Aug. 1, 1950 FUEL SUPPIiY SYSTEM FOR INTERNAL- COMBUSTION ENGINES Stanley George Hooker, Derby, and David Havelock Ballantyne, Lan

land, assignors to gho, near Blackburn, Eng- Roils-Royce Limited, Derby,

England, a British company Application April 8, 1947, Serial No. 740,253

In Great Britain April 1, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires April 1, 1966 17 Claims. 1

This invention relates to fuel-supply systems for internal-combustion engines of the type in which the fuel is supplied to the engine by a group of pumps capable of supplying adequate fuel for normal engine requirements even if one of the pumps in the group is inoperative, and has for its object to provide an improved construction and arrangement whereby the reliability of the supply of fuel to the engine is enhanced; this is particularly important in the case of jet propulsion engines where it has been considered desirable hitherto to duplicate the pumps, and a further object of this invention is to provide means whereby a useful degree of safeguarding is provided for installations comprising twin fuel pumps.

The invention relates to that kind of fuel-supply system of the type described above in which the rate of delivery of the fuel pumps is controlled by a hydraulic pressure system arranged so that variations in the hydraulic pressure of the system produce variations in the pump delivery, for example, an increase of pressure in the system may cause a decrease in pump delivery and vice versa. The arrangement may be such as to maintain a constant delivery pressure from the pumps, and for this purpose the pressure in the hydraulic pressure system is regulated by valve means actuated in accordance with the delivery pressure. When the invention is used in connection with aircraft engines the pressure in the hydraulic pressure system may be varied in accordance with the atmospheric pressure to adjust the pump delivery pressure in accordance with the altitude requirements of the engine.

According to the present invention there is provided for an internal combustion engine, a fuel supply system of the kind set forth which comprises two or more pumps delivering to a common point, means associated with each pump for regulating its delivery, a hydraulic control system common to the regulating means for independently adjusting each of them and means for isolating one or more regulating means from the common control system whereby one or more of the pumps is or are put out of operation and the other or others adjusted to increase its or their delivery.

According to a feature of the invention there may be provided for an internal combustion engine, a fuel system of the kind set forth which comprises two pumps delivering to a common point, each of which is capable of supplying substantially the full requirements of the engine, means associated with each pump for regulating its delivery. a hydraulic control system common to the regulating means for independently adjusting each regulating means from the common control system whereby one of the pumps is put out of operation and the other adjusted to increase its delivery.

A preferred embodiment of the invention will now be described, by way of example, as applied to the fuel-supply system for a gas turbine jetpropulsion engine for an aeroplane. The description is made with reference to the accompanying drawings whereof:

Figure 1 is a diagrammatic tem as a whole, and

Figure 2 is a diagrammatic view, to an enlarged scale, of that part of the system with which this invention particularly deals.

Attention is directed to Figure 1 where the gas turbine jet-engine, which is generally indicated by the reference numeral 5, comprises compressor 6, combustion chambers l, turbine 8 and jet pipe 9. Fuel is delivered to the combustion chambers from a tank in by way of a filter H to a control. generally indicated by the dotted outline H, a shut-0E cock l3, and pipe line IS. The fuel is delivered under pressure by a pair of pumps which form a part of control 12 as will be explained in detail hereinafter. The two pumps are independently driven, for instance, they may both be driven independently from the engine 5 or one may be driven from the engine and one driven, for example, by an electric motor.

As is clear from Figure 2 the pumps l6 and ill are of the swash-plate type and each comprises a pump body It. a plurality of plungers it therein, a spring 20 for each plunger urging it against the swash-plate 2d, a common inlet 22 to the plunger barrels and a common outlet 23 therefrom. The swash-plate it is angularly adjustable by a linkage 24 to vary the effective stroke of the plungers-and hence the delivery of the pump. Each pump is driven as mentioned above by a shaft 25.

view of the fuel sys Each pump l6, H receives a supply of fuel at low pressure from tank In by main pipe 26 and branch pipes 21 and they both deliver the fuel under a high pressure to a main pipe 28, a throttle valve 29, and so to the engine 5. The throttle valve 25 gives the desired control of the engine in'the usual manner, being adjusted for opening by lever 30.

From the common outlets 23 of each pump there is a branch pipe 3| connecting them to main pipe 28 and it will be observed that each branch of them and means for isolating a Both sides of ram 34 communicate with port 33,

one (the spring-blessed side) through a restricted orifice 36 and the other without impediment.

With this arrangement the ram 34 will be moved by the pressure difl'erential existing acrossthe ram, such movement to the left causingan increase in pump delivery (and hence in pumpdelivery pressure assuming that the throttle 30 remains in fixed position) whilst movement to the right results in a reduction in pump delivery and pressure.

The pressure on the spring-blessed side of each ram 34 is determined by an outflow valve 4| which is urged to its closed position by a spring 42. The valve 4| communicates with each device 32 by a pipe line 44, whilst pipes 3i carrying the fuel delivery pressure, communicate with a common branch 31 leading to cylinder 33 whose piston 33 operates on an arm 40, carrying the movable member of valve 4|. The arm 40 is fulcrumed on a sealing diaphragm l4 and is adjusted by a barometric capsule 43, which varies the loading of the spring 42 with changes of operational altitude of the aircraft. The arrangement above outlined (which has been hitherto known and used) is such that when a pre-determined pressure is reached within the cylinder 35, l. e. the fuel pressure delivery reaches a certain value. piston 39 raises arm ill against spring 42 to open valve 4 l.

Co-related with the outflow through valve 4| is the size of the restricted orifice 36: thus, it the outflow at 4| increases the pressure drop across 36 increases and the pressure in device 32 drops and piston 34 is moved to the right to decrease the stroke of the pump, its delivery and consequently its pressure. A reduction of delivery pressure results in piston 39 reducing its operative load against spring 42 and valve 4| moves towards its closed position to cause an appro-' priate increase in pressure in pipes 44, to increase to, and then maintain at, a desired pump delivery pressure. Fuel flowing through valve 4| is returned to inlet pipe 21. If the pressure of the pump falls the opposite sequence of operations is followed, valve 4| closing so that pump delivery pressure is raised.

In addition the spring-blessed side of each ram 34 is provided with an outlet 45 controlled by the diaphragm-controlled valve 46. The diaphragm 41 is subject to the centrifugal pressure generated in the pump chamber l8 and it is arranged that at a pre-determined rotational speed of the pump this pressure opens valve 46 to enable fuel to escape from the control system, and to result in a reduction of the pump stroke and its delivery pressure. The outflow through the valve 46 returns to the inlet side 22 of the pump. In addition a spring 48 normally loading the valve 46 on to its seating may be compressed by fuel-pressure loading on the valve 46 so that the valve lifts, when a pre-determined pump delivery pressure is communicated to it through a restricted passage 36, whereby the valve 46 also operates as a relief valve.

The functioning of the pump outlined above is well known and does not itself constitute a feature of the present invention.

It will be appreciated that the provision of an hydraulic pressure system constituted by pipes 44 and control valve 4|, common to both pumps l6 and I1, results in the pumps being controlled similarly and simultaneously.

Each of the pumps I6, I! is made of such capacity that it can supply substantially the full power requirements of the engine 6 if the other pump is for any reason rendered inoperative.

. The possible sources of failure in this system are (a) the control valve 4| or either of the diaphragm-controlled valves 46, (b) the hydraulic Pressure pipes 44 may be punctured (0) either pump l6, I! may fail mechanically; with systems previously used, if any of these failures should occur it results in excessive leakage of pressure-fuel from the spring-biased side of the associated control 32 so that the over-all output of the pumps is reduced to a dangerous extent.

According to this invention an isolating control is provided between pump l1 and the outflow valve 4|, such control being arranged to permit closure of pipe 44 leading from said pump, by the pilot of the aircraft, at will. Any suitable form of shut-oil valve or cock 43 is used. operated mechanically or by a solenoid or any other form of remote control, and this provides adequate safeguards against the possible source of failure mentioned above, as now about to be described.

In normal operation when the isolating valve 49 is open so that the pumps I6, l'l are similarly and simultaneously controlled, the outflow valve 4| controls devices 32 so that it adjusts the stroke '01 each of the pumps so that each supplies approximately half the total requirements of the engine 5. This control is effected by the devices 32 which are adjusted with variation in the rate of discharge through outflow valve 4|-the discharge being controlled by the piston 33 dependcut on the prevailing delivery pressure of the pumps. When the isolating valve 43 is closed, the hydraulic pressure will be equal on both sides of the ram 34 of the isolated pump H, the pressure on the spring biased-side being no longer determined by the outflow valve 4|, and the spring 35 will set the isolated pump II to give its maximum delivery. This delivery may be appropriate to the maximum permissible speed of the engine, or a governor-control from the engine may be fitted to the pump so that when it is operating to supply the engine on its own the stroke of the pump is automatically adjusted to give the maximum permissible speed of the engine.

when the isolated pump I1 is thus delivering the full fuel-requirement of the engine 6, the pressure on the delivery side of the pump is applied by pipe 31 to cylinder 38 so that outflow valve 4| is operated to reduce the controlling hydraulic pressure on the ram 34 of pump l6 and thereby reduce the delivery of this pump to zero so that the whole of the engine requirements are provided by pump Supp ing now that the outflow valve 4| sticks open, the pilot on appreciating that there is a failure in the system will immediately close the isolating valve 43. The conditions just described are then created and the isolated pump I1 provides the full requirements of the engine as determined by the pilots setting of the throttle valve 26.

If the valve 46 on the pump I. should stick open the decrease in the controlling pressure on the hydraulic rams 34 will become apparent to the ilot and closure of valve 46 again restores the conditions in which the isolated pump l1 effects the full requirements of the engine as described above.

If valve 48 on the pump .i'l should stick open, a

closure of the isolating valve 49 prevents the resulting loss of operating hydraulic pressure from affecting the outflow valve 4| which maintains its normal control, and the unisolated pump It is thereupon adjusted so that it delivers all the fuel requirements of the engine; the isolated pump ll reduces its delivery or comes to its zero delivery setting owing to the loss of its controlling hydraulic pressure through its valve 48. It will thus be seen that failure by any of the valves sticking open is adequately catered for.

If the pipe 44 connecting the two devices 32 to the outflow valve should be punctured above the valve 45, there is immediately a decrease in the controlling pressure of the devices and closure of the isolating valve 49 brings the isolated pump. II into action in the manner already described to supply the full requirements of the engine 5. If the puncture is'below the isolating valve 49, closure of the isolating valve 49 causes the pump is to be adjusted by the hydraulic control system to supply the full requirements of the engine 5.

In the case of a mechanical failure of either of the pumps i6, i1, so that its delivery is reduced or ceases, the outflow valve control would operate in a direction to increase the joint de-' livery of the two pumps, but as it would be unable to effect this, the closure of the isolating valve 49 would bring one or other pu'np into operation to give the full delivery. If it is the isolated pump I! which has failed, the unisolated pump iii would continue to function normally giving the full delivery under the control of the relief valve It. If, on the other hand, it is the unisolated pump it which has failed, the isolated pump ll then continues to supply the full requirements of the engine.

In order to avoid the possibility of a pump which has failed, e. g. due to shearing of a shaft 25, being driven or motored by pressure fuel supplied by the remaining pump, there may be inserted in the delivery pipes 3i non-return valves which close in the event of pressure failure in either line 3i.

Whilst this invention has been described in detail in connection with a particular form of fuel pump. it will be appreciated that it can be applied with suitable modifications to any other form of pump in which the rate of delivery is controlled in accordance with hydraulic pressure which may in turn be controlled in accordance with delivery pump-pressure or in any other manner.

We claim:

1. For an internal combustion engine, a fuel supply system of the kind set forth comprising a plurality of pumps delivering to a common point, means associated with each pump for regulating its delivery, an hydraulic control system common to the regulating means for independently adjusting eachof them and means for isolating at least one regulating means from the common control system whereby at least one of the pumps is put out of operation and the remainder adjusted to increase delivery.

2. For an internal combustion engine, a fuel supply system of the kind set forth comprising two pumps delivering to a common point, each oi. which is capable of supplying substantially the full requirements of the engine, means associated with each pump for regulating its delivery, an hydraulic control system common to the regulating means for independently adjusting each of them and means for isolating a regulating means from thecommon control system whereby one of the pumps is put out of operation and the other adjusted to increase its delivery.

3. A fuel supply system according to claim 1 in which the common hydraulic control system incorporates an outflow valve, the opening of which is adjustable by the delivery pressure of the pumps, through which the fuel passes from the delivery line of each pump by way of a restricted orifice, and means responsive to the pressure drop across each of the restricted orifices for regulating the associated pump.

4. A fuel supply system as claimed in claim 1,

wherein the isolating means comprises a manually operated valve.

5. A fuel supply system as claimed in claim 1, in which the regulating means comprises a pistonand-cylinder device on each pump communieating by a common pipe line with the outflow valve, the isolating valve being provided inone of said pipe lines.

6. For an internal combustion engine, a fuel supply system comprising a main fuel delivery pipe; a plurality of adjustable capacity fuel pumps; fuel delivery connections, one between each of said pumps and said main fuel delivery pipe; capacity adjusting means for each of said pumps, each such means including a chamber and a member actuated by hydraulic pressure in said chamber a main regulating pressure interconnecting pipe: hydraulic regulating pressure connections, one between each of said chambers and said main interconnecting pipe; means for delivering liquid under pressure into the system constituted by said main interconnecting pipe, said regulating pressure connections, and said chambers, regulating means for defining the pressure in said system so as normally to actuate said capacity adjusting means together in accordance with such pressure; and means for hydraulically isolating at least one of said chambers from the hydraulic pressure regulated by said regulating means, thereby to permit independent actuation of at least one of said capacity adjusting means.

7. For an internal combustion engine, a fuel supply system comprising a main fuel delivery pipe; a plurality of adjustable capacity fuel pumps; fuel delivery connections, one between each of said pumps and said main fuel delivery pipe; capacity adjusting means for each of said pumps, including a chamber and a member actuated by hydraulic pressure in said chamber; regulating pressure connections to each of said chambers; a main interconnecting regulating pressure pipe connected to each of said regulating pressure connections; means for supplying liquid under pressure to said interconnecting pipe, and said regulating pressure connections and said chambers; means for regulating the pressure in said inter-connecting pipe, thereby normally to actuate said members together in accordance with said pressure, and means for hydraulically isolating at least one of said chambers from said interconnecting pipe.

8. For an internal combustion engine, a fuel supply system, comprising a main fuel delivery pipe; a plurality of adjustable capacity fuel pumps; fuel delivery connections, one between each of said pumps and said main fuel delivery pipe; capacity adjusting means for each of said pumps, each such means including a chamber and an actuating member subjected to hydraulic regulating pressure ,in said chamber, such that reduction of saidregulating pressure is operative to decrease the capacity of the associated. pump; a main regulating pressure interconnecting pipe; regulating pressure connections, one between each of said chambers and said main interconnecting pipe; means for regulating hydraulic pressure in said interconnecting pipe, thereby normally to effect capacity adjustment of the pumps together in accordance with such pressure, and means for isolating one of said chambers from said main interconnecting pipe.

9. For an internal combustion engine, a fuel supply system comprising a main fuel delivery pipe; a plurality of adjustable capacity fuelpumps; fuel delivery connections, one between each of said pumps and said main fuel delivery pipe; capacity adjusting means for each of said pumps, each such means including an actuating member subjected to a first hydraulic pressure in a first chamber on one side of said member derived from the discharge pressure of the associated pump and a second hydraulic pressure in a second chamber on the other side of said member, derived from said discharge pressure through flow restricting means, each of said capacity adjusting means being operative to decrease the capacity of its associated pump on increase of said pressure diiference; liquid flow connections to each of said second pressure chambers; a main interconnecting liquid flow pipe connected to each of said liquid flow connections; valve means regulating the outflow from said main interconnecting pipe, whereby said second hydraulic pressure is defined by said outflow correlated with the flow through said restricting means normally to adjust the capacity of the pumps together in accordance with such second pressure; and means for hydraulically isolating at least one of said liquid flow connections from said main interconnecting pipe.

19. For an internal combustion engine, a fuel supply system comprising a main fuel delivery pipe; a plurality of adjustable capacity fuel pumps; fuel delivery connections one between each of said pumps and said main fuel delivery pipe; capacity adjusting means for each of said pumps, each such means including a chamber and an actuating member subjected to hydraulic regulating pressure in said chamber, such that reduction of said regulating pressure is operative to decrease the capacity of the associated pump; a main regulating pressure interconnecting pipe; regulating pressure connections, one between each of said chambers and said main interconnecting pipe, means for regulating hydraulic pressure in said regulating pressure interconnecting pipe as a function of pressure conditions in said main fuel delivery pipe, thereby normally to effect capacity adjustment of the pumps together in accordance with such pressure to maintain a predetermined pressure condition in 'said main fuel delivery pipe; and means for isolating one of said hydraulic pressure actuating members from said main regulating pressure interconnecting pipe, whereby capacity adjusting means remaining connected to said main interconnecting pipe is efiective to maintain said predetermined pressure conditions in said main fuel delivery pipe.

11. For an internal combustion engine, a fuel system comprising a main fuel delivery pipe; two adjustable capacity fuel pumps, each capable of supplying normal engine requirements; fuel delivery connections, one between each of said pumps and said main fuel delivery pipe: capacity adjusting means for each of said pumps, each such means including a chamber and an actuating member subjected to hydraulic regulating pressure in said chamber, such that reduction of said regulating pressure is operative to decrease the capacity of the associated pump; a main regulating pressure interconnecting pipe; regulating pressure connections one between each of said chambers and said inain interconnecting pipe; means for regulating hydraulic pressure in said interconnecting pipe as a function of pressure conditions in said main fuel delivery pipe, thereby to normally effect capacity adjustment of the pumps together in accordance with such pressure to maintain a predetermined pressure condition in said main fuel delivery pipe: and means for isolating one of said hydraulic pressure actuating members from said main interconnecting pipe, whereby the remaining actuating member is effective to maintain said predetermined pressure conditions in said main fuel delivery pipe.

12. For an internal combustion engine, a fuel supply system comprising a main fuel delivery pipe, a plurality of adjustable capacity fuel pumps, fuel delivery connections one between each of said pumps and said main fuel delivery pipe, capacity-adjusting means for each of said pumps each such means including an actuating member subjected to the pressure difference between a first hydraulic pressure derived directly from the discharge pressure of the associated pump in a first chamber on one side of said member and a second hydraulic pressure in a second chamber on the other side of said member, each of said capacity-adjusting means being operative to decrease the capacity of its associated pump on an increase of said pressure difference, a main regulating pressure interconnecting pipe, regulating pressure connections one between the second chamber of each capacity-adjusting niean's and said main interconnecting pipe, means for isolating at least one of said capacity-adjusting means from said main interconnecting pipe, pressure regulating means normally operative to maintain the hydraulic pressure in said main interconnecting pipe at a value preselected in accordance with the fuel requirements of the engine.

iii. A fuel supply system according to claim 12, comprising a first duct between the discharge branch pipe of each pump and the flrst chamber ofthe capacity-adjusting means for that pump, a second duct between the fuel delivery connection of each pump and the second chamber of the capacity-adjusting means for that pump, liquid flow restricting means in each of said second ducts, resilient means for each capacityadjusting means urging the actuating member into said first chamber, an outflow valve for said main interconnecting pipe and means for adjusting the outflow area of said outflow valve in accordance with pressure conditions existing in said main fuel delivery pipe.

14. A fuel supply system according to claim 13 wherein said means for isolating at least one of said capacity-adjusting means is a manually operated valve.

15. A fuel supply system according to claim 14 wherein each capacity-adjusting means comprises a piston and cylinder device whereof the cylinder is connected at one end to said first duct and at the other end to said second duct and whereof the piston is the actuating member and is spring-loaded towards the end of the cylinder connected to said first duct.

16. For an internal combustion engine, a fuelsupply system comprising a main fuel delivery pipe, two adjustable-capacity fuel pumps each capable of supplying normal engine requirements, discharge delivery connections one between each of said pumps and said main fuel delivery pipe, capacity-adjusting means for each of said pumps each such means including an actuating member subjected to the pressure difiference between a first hydraulic pressure derived from the discharge pressure of the associated pump in a first chamber on one side of said member and a second hydraulic pressure in a second chamber on the other side of said member, each of said capacityadjusting means being operative to decrease the capacity of its associated pump on an increase of said pressure difference, a main regulating pressure interconnecting pipe, regulating pressure connections one between the second chamber of each capacity-adjusting means and said main interconnecting pipe, means for isolating at least one of said capacity-adjusting means from said main interconnecting pipe, means normally operative to maintain the hydraulic pressure in said main interconnecting pipe at a value preselected in accordance with the fuel requirement of the engine.

17. For an internal combustion engine, a fuel supply system comprising a main fuel delivery pipe, two adjustable-capacity fuel pumps each capable of supplying an engine requirement greater than half the engine requirement at full power, fuel delivery connections one between each of said pumps and said main fuel delivery pipe, capacity-adjusting means for each of said pumps each such means including a piston and a cylinder, a first duct between one end of said cylinder and the associated fuel delivery connection, a second duct between the other end of said cylinder and said associated fuel delivery con nection, flow restricting means in said second duct and a spring-load urging said piston towards said one end of said cylinder, said capacity-adjusting device being operative to increase the capacity of its associated pump on movement of said piston towards said one end of said cylinder, said fuel system further comprising a main regulating pressure interconnecting pipe, regulating pressure connections between said other ends of said cylinders of each of said capacity-adjusting means and said main interconnecting pipe, a manually-operated isolating valve in said main interconnecting pipe between said connecting pipes, an outflow valve for said main interconnecting pipe, a valve-member operative to adjust the outflow area of said Outflow valve, a spring load on said valve member urging it towards its closed position, a valve-control cylinder, a piston in said valve-control cylinder operatively connected to said valve member to urge it away from said closed position on increase of hydraulic pressure in said valve-control cylinder, and a duct between said valve-control cylinder and said main fuel pipe.

STANLEY GEORGE HOOKER. DAVID HAVELOCK BALLANTYNE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Snader et a1 Oct. 20, 1942 

